Content Distribution
Traditional barriers between broadcast television, direct broadcast satellite networks, cable systems, MMDS, terrestrial network operators, internet technologies, dedicated point to point wide area networks, and general purpose computing have begun to rapidly dissolve. In particular, these technologies are migrating into an integrated whole. The development of interconnection architectures enables these emergent home and portable multimedia entertainment and commerce systems to grow in a manner analogous to the evolution of centralized and distributed computing, transmission, and storage architectures. Current systems are utilized in the distribution of interactive entertainment, all forms of electronic commerce, digital music downloads, digital video downloads, pay-per-view, pay-per-play audio, near or true video-on-demand, near or true audio-on-demand, near or true books-on-demand, software downloads and distribution, interactive advertising, gaming, home banking, education, and regionalized or end user targeted weather and news, among others.
Multimedia portable and home recording and playback technology has similarly evolved with the advent of high-density ROM discs, read and write CD or DVD Discs, high density RAM, and magnetic disc technology. One form of emergent media, known as DataPlay (manufactured by DataPlay, Inc. of Boulder, Colo.), is a portable, physically compact, robust and affordable removable disc media system predicated on DVD technology. DataPlay utilizes various forms of digital rights management to protect content and facilitate commerce of recorded content. For example, DataPlay discs including such content as music or video may be physically distributed under the protection of the digital rights management scheme protecting the content from unauthorized copying or accessing.
One problem within the current art is the extensive capital investment required with new CD, DVD, and other optical disc process lines. Each new generation of optical disc has required extensive investment in process development, manufacturing technology, manufacturing equipment, and related facilities and support. This is especially true as we presently witness the consolidation of present manufacturing lines amongst content providers such as record companies who are trying to mitigate capital expenditures and overhead costs.
Another limitation associated with current content distribution schema are the inherent limitations within the present Digital Rights Management (DRM) as implemented with digital schemas, i.e., advances in processing power available for decryption, collaborative distributed processing efforts such as those utilized to break DES (digital encryption system), human disclosure factors as witnessed by the publication of standard DVD keys, combined with the fact that content is often available in an unencrypted format rendering the cryptographic analysis of the key possible.
The DataPlay disc and other forms of pre-recorded ROM type media, therefore, are limited, to the physical distribution of the discs and recorded content. In addition, the DataPlay art and other forms recordable media are limited by the bandwidth and long latencies inherent to Internet content distribution methodologies. Without immediately available content, currently unavailable to users utilizing such recording media, the DataPlay and other recordable media require users to wait for content prior to recording. Finally, as DataPlay and other recording devices have used standard or publicly available methodologies in the reading or writing device, recorded content is no longer safe from unauthorized access.
Optical Disc Technology
The introduction of the Compact Digital Audio Disc (CD-DA) in 1982 unleashed a transformation in the way consumers obtain and store audio content. In order to achieve the CD's low cost, high reliability (low bit error rates), and consistent audio output quality, many revolutionary technologies had to simultaneously achieve fruition. In specific, the advent of long life double heterojunction AlGaAs laser diodes, low cost diffraction limited optics (diffraction gratings, polarization beam splitters, quarter wave plates, first surface mirrors, and collimating/cylindrical lenses), and high resolution optical scanning/position encoding, employed in conjunction with high resolution digital signal quantization (analog-to-digital converters), analog signal reconstruction (digital-to-analog converters), high stability, low run-out, servo drives and low cost polycarbonate disc manufacturing materials and processes were all necessary to facilitate this revolution in consumer audio distribution.
The current art requires an easy migration path to higher capacity discs utilizing shorter wavelength long life laser diodes (such as 400-410 nanometer (nm) devices), as well as a system compatible with reading both higher capacity discs utilizing shorter wavelength long life laser diodes (such as 400-410 nanometer (nm) devices) and legacy DVDs and CDs.
Modern CDs store about 1 million bits/mm2 on a 12 cm disc. Information is encoded on “pits” within the disc impressed upon a polycarbonate layer. Pits are 0.6 um wide arranged on tracks spaced 1.6 um apart. 22,188 tracks are arranged on each disc over an active surface disc 35.3 mm wide. The bit rate from a disc is 4.3218 megabits/second resulting from a circular linear velocity read rate of 1.2 m/sec and, subtracting for overhead, error correction, and tracking information affords an audio bit stream of 1.41 megabits/second i.e. two channels of audio (stereo) of 16 bit resolution per sample at 44.1 KHz for 4,440 seconds. Thus of the approximately 15.5 billion bits of information on a modern CD, 6.26 billion are available for actual audio information and the balance are allocated for overhead. Thus one limitation within the current art is the high ratio of overhead to data (audio) bits—currently 15.5/6.2, or equivalently 2.5:1. The CD family has witnessed many new members along the years including CD-ROM (1984), CD-i (1986), CD-WO (1988), Video-CD (1994), and CD-R/W (1996). Other limitations within the CD art include low total storage (from 783 to 867 megabytes), low output bandwidth (176 kilobytes/second standard 1×), and limited file format flexibility. While the bandwidth has been improved with a new generation of high velocity readers (52×+), this is fundamentally the outgrowth and deployment of Digital Versatile Disc technology discussed below.
Again, owing to limitations with the CD's storage density and bandwidth, an improved technology was required to support high resolution video for sustained periods of time (e.g. single movies) along with larger quantities of data. In 1997, the Digital Versatile Disc (or Digital Video Disc) was unleashed, based upon the fundamental concepts employed in CD design, albeit with a somewhat shorter wavelength laser diode (635 or 650 nm as compared with a CDs 780 nm laser), improved optics (a Numerical Aperture NA of 0.6 as compared with the CDs NA of 0.45), servo drive (3.49 m/sec on a single layer DVD, 3.84 m/sec on a dual layer DVD as compared with the CDs 1.2 m/sec), bit density improvements including track to track spacing (0.74 um DVD pitch spacing versus a CD's 1.6 um spacing) and linear bit density (DVD single layer 0.40/1.87 um min/max—DVD dual layer 0.44/2.05 um min/max), multiple layers (optional), multiple sides (optional) and mandatory sophisticated microprocessor decoding and error correction. The resultant performance specifications are a recording bit density of 7× improvement from the CD (DVD 7 million bits/mm2 versus the CD's 1 million bits/mm2), a commensurate 7× storage density per DVD layer of 4.7 billion bytes. It should be noted that reduced DVD “pit” size actually accounts for an area density improvement of only 467%, and the remainder of the bit density improvement is from highly improved data encoding and error correction techniques.
A fundamental departure from the CD is found in the universal file structure of the data on a DVD, which is truly near random access (pseudo addressable) data storage. This capability combined with real-time microprocessor interactivity should allow DVD to become the dominant media in video distribution and storage (over VHS and laser disc) along with audio, data storage, and software distribution (over the CD). DVDs are divided amongst six types (specification books A through E as known in the industry)—DVD-ROM, DVD-Video, DVD-Audio, DVD-R, DVD-R/W, DVD-RAM.
DVD disc capacities are not linear per layer. Since the optical system must be refocused to read the outer semi-reflective or inner fully-reflective (embedded layer), signal-to-noise losses occur when reading the inner layer. To compensate the inner embedded track is read at slightly higher rate with a lower bit density. Hence another limitation within the current art is the limited signal to noise ratio achievable with current 635/650 nm laser diodes and multi-layer DVD disc technology. For reference a DVD-5 single side/single layer disc holds 4.7 billon bytes, and as expected DVD-10 double side/single layer disc holds 9.4 billion bytes; a DVD-9 single sided dual layer disc holds 8.5 billion bytes and a DVD-18 dual sided, double layer disc holds 17 billion bytes. Output total bit rates are 26.16 million bits/sec and the maximum out data rate is 11.08 million bits second—for a net aggregate coding overhead ratio of 2.36 (slightly improved from CD overhead of 2.5:1). Thus another limitation within the current art is the still low coding efficiency of DVD technology. Yet another limitation of DVD is found in the low output data rate of 1.385 megabytes/second.
Both pre-recorded and user-recorded data may be included on a single disc. However, a typical DataPlay disc is 32 mm in diameter and holds only about 500 MB of data. Thus one limitation of DataPlay technology is the low total storage capacity of the DataPlay Device. DataPlay devices are presently capable of 0.97 megabytes/second sustained transfer rate of written data and 0.79 megabytes/second transfer rate of ROM data. Thus another limitation of DataPlay devices is their total sustainable read/write bandwidths. Furthermore, because DataPlay technology is based upon DVD technology, other limitations within the current DataPlay technology are the limited signal to noise ratio achievable with current 635/650 nm laser diodes along with the still low coding efficiency.
In order to achieve reasonable laser diode power consumption levels, DataPlay devices utilize unprotected pits and land surfaces to encode data, making them highly vulnerable to damage by handling and contamination. In contrast, standard DVDs (see, ECMA-267 Standard, 3rd Edition, April 2001, which is incorporated by reference in its entirety) utilize two 0.6 mm polycarbonate layers that are bonded together with the data layers protected on the internal surfaces, thus forming a 1.2 mm total DVD thickness. This methodology was developed in response to limitations found in the CD's placement of the data layer near the top surface, where it is extremely vulnerable to damage. Thus another limitation within the current DataPlay art is the use of thin coated surfaces, making them highly vulnerable to damage and debris.
As a direct result of utilizing thin coated surfaces, DataPlay devices incorporate a protective housing for the data surfaces. The housing requires a moveable mechanical assembly to expose an area of the disc for reading and writing of the encoded data. Inherently, all mechanical devices have a lower reliability than a system with no moving parts due to normal wear and tear, along with a greater susceptibility to handling and environmental issues. Further a protective assembly adds cost and complexity to the manufacturing processes, non-recurring design, tooling costs, and per item manufacturing costs. Thus yet another limitation within the current DataPlay art is the need for a protective housing.
Thin coated data encoding surfaces, such as those utilized in DataPlay Devices are highly susceptible to contamination. Since encoded data pits are at or near the focal plane of the read or write optical beam, any contamination residing on the surface of the disc becomes extremely problematic. While the DataPlay device utilizes a protective housing, it requires opening for the reading or writing the disc. As such it is exposed to the external environment within the Datplay player and any internal contamination or humidity. Contamination is cumulative over the life of the disc and contaminants from one DataPlay player may be deposited within another player by utilizing a disc or discs within multiple players. Thus another problem within the current art is that thin coated discs always suffer from a higher bit error rate due to contamination.
As data densities continue to increase, individual “bits” will be encoded on ever smaller surface areas within the disc. Small particulate matter, condensation molecules, and other forms of contamination will be able to induce multi-bit errors that require more sophisticated error correction techniques. For a given size and efficacy of a given contaminant, the number of successive bit errors will be increased as corresponding bit densities increase, requiring more bits to be reserved for bit error correction and reliable tracking, thus reducing the amount of user data available on a given disc. Hence, yet another problem with thin coated discs is the requisite additional error correction bits and encoding scheme, limiting the percentage of useable data bits, along with reducing or eliminating the benefits of increased bit encoding density on the disc.
Thin disc substrates are less susceptible to tilt relative to the read/write optical device. Thus DVDs with their 0.6 mm data to surface distance are less susceptible to tilt errors than CDs which have a 1.2 mm data to surface distance. Conversely, the 1.2 mm CD distance allows the laser beam to be more out of focus at the surface than is that of the 0.6 mm DVD. DVDs are thus required to have a more sophisticated error correction technique to compensate. The thickness of the protective surface is restricted by the optical losses within the protective material. Optical losses are due to surface reflection, absorption, and internal scatter. Clearly the higher the losses the more optical power required for a given bit error rate—translating to increased laser diode or other optical source power consumption and decreased reliability and lifetime. Thus another limitation within the current art is the high optical losses within protective disc coatings, requiring higher power optical sources for given bit error rates. Yet another limitation within the current art is the error due to tilt, which may limit the thickness of practical protective coatings.
Losses within protective disc optical coatings are not the only losses within the optical laser read or write path. Typically the optics within a disc or DataPlay player have substantive losses, up to 75% or more of the laser diode or other source output photons are lost in the read or write optical path. This is due to limitations within the optical materials themselves, the ability to effectively deliver the photons with an optimal spot beam size (energy disc), or the ability to collect reflected/transmitted photons from the data bit surfaces on the disc. Thus another problem within the current art is the lossy optical delivery and collection optics within DataPlay and other optical disc players.
Future applications will require multiple high-resolution movies and/or multiple audio albums on a single storage disc. While the inherent manufacturing costs of prior art CDs and DVDs are modest, the transportation and distribution expenses of single movie or a limited number of audio albums on a single disc prohibits the pre-sale distribution of key encrypted content discs for subsequent sale, i.e. discs are shipped to consumers and unlocked if and when desired for pay per play or purchase. Thus another limitation within the current art is the limited storage density of DVD discs.
The ubiquitous proliferation of illegal DVD decryption software has lead to an industry wide concern of piracy. This is also true of audio content. Further as more consumers have access to broadband Internet links the threat of piracy ever increases. While it may be possible to police the future Napsters of the world, it will not be possible to prohibit piracy between consenting parties. Encoding techniques and other forms of digital rights management fail because of the always-present human element within the system. Thus another limitation within the current art is the limitations of digital encryption technology.
It is therefore desirable to provide secure methods and apparatus for broadcast transmission and high capacity storage of content.